Thomas Aquinas’ arguments for the existence of God and His attributes

Thomas Aquinas was a Dominican friar who lived from 1225-1274. He wrote many important works, including the Summa Theologica, The Summa Contra Gentiles, and Commentaries on the works of Aristotle. He had many important ideas, in particular the Quinque viae, or “The Five ways”. These were five proofs he made for the existence of God.

In the first of these five ways, he uses many concepts established by the Greek philosopher Aristotle. He uses Aristotle’s concept of motion (change), which means going from potentiality to actuality. For example, a soccerball may have the potential to make a goal, but it’s potential to be in the goal needs to be actualized by something else, like one of the players. Something, said Aristotle, cannot actualize it’s own potential. Something outside it must.

Aquinas said that in a given moment, anything going from potentiality to actuality must be actualized by something else. But, the other object that is actualizing the first object also needs to be actualized in that moment, and the third object as well, and so on. Aquinas used an example involving a hand using a stick to move a stone. The stone is having it’s potential actualized by hand moving the stick which is in turn moving a stone. If there was no hand, the series breaks down. In fact, the hand is moved by other things as well, so the series continues. For a series of things being actualized in a given moment, there must be a first member in the series, he says. It cannot go to infinity, or nothing would happen at all.

Aquinas also used logic to argue for the existence of many of God’s attributes. One of the attributes he derived was God’s all-powerfulness, also known as Omnipotence. Aquinas argued that the first member in a series involving change must be unmoved or unchanging. If the first member of a series were moving or changing, it would be moving from potentiality to actuality, which must be done by something else and thus is not the first member. The only way, Aquinas said, to stop this regress is a being that does not need to be actualized. It must be pure actuality, or act. With no potency to realize, this being could not move or change. This being, Aquinas said, we call God. Aquinas used the term “Unmoved Mover” to refer to God at times.

Aquinas then proceeded to derive certain attributes about God from his conclusions about Him. He concluded that God must be all-powerful using an Aristotelian principle: A cause cannot give what it does not have. Aristotle said that the cause of a feature must possess that feature either formally or eminently. An example of possessing a feature formally is a wet sponge. A wet sponge is both wet and can make other objects wet. An example of an object possessing a feature eminently is a sprinkler system, which may not be wet, but has the potentiality to produce water and make other things wet.

The Unmoved mover (God) is the source of all change, of things acquiring the attributes they have. Therefore, God possesses all these attributes. This means that God is all-powerful if He has all these attributes


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